diff --git a/flake.lock b/flake.lock
index 8e967f10..21e8c939 100644
--- a/flake.lock
+++ b/flake.lock
@@ -25,6 +25,7 @@
     "elmer": {
       "inputs": {
         "csa": "csa",
+        "flake-compat": "flake-compat",
         "flake-utils": "flake-utils_2",
         "mmg": "mmg",
         "mumps": "mumps",
@@ -33,11 +34,11 @@
         "parmmg": "parmmg"
       },
       "locked": {
-        "lastModified": 1724740583,
-        "narHash": "sha256-XUFJ3JDbW0IULg2bS7mvoy7n8EcAtHy/hTQ7thuQ+CU=",
+        "lastModified": 1724765091,
+        "narHash": "sha256-gK6dfL22Zmwkc2eFcvV1dwLdmQmH6UB6Ve/HnzZ+mNA=",
         "owner": "ElmerCSC",
         "repo": "elmerfem",
-        "rev": "23b6c208c4f0e25f5d3b69fca602c432d4ba1da7",
+        "rev": "cd0369d1ff2beab73ddf8ec4ba007353a4456d7a",
         "type": "github"
       },
       "original": {
@@ -47,6 +48,20 @@
       }
     },
     "flake-compat": {
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "revCount": 57,
+        "type": "tarball",
+        "url": "https://api.flakehub.com/f/pinned/edolstra/flake-compat/1.0.1/018afb31-abd1-7bff-a5e4-cff7e18efb7a/source.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://flakehub.com/f/edolstra/flake-compat/1.tar.gz"
+      }
+    },
+    "flake-compat_2": {
       "flake": false,
       "locked": {
         "lastModified": 1696426674,
@@ -306,7 +321,7 @@
     "root": {
       "inputs": {
         "elmer": "elmer",
-        "flake-compat": "flake-compat",
+        "flake-compat": "flake-compat_2",
         "flake-utils": "flake-utils_6",
         "nixpkgs": "nixpkgs_2"
       }
diff --git a/flake.nix b/flake.nix
index 2837e93b..1a53e0df 100644
--- a/flake.nix
+++ b/flake.nix
@@ -48,6 +48,8 @@
             wsl.elmer.enable = true;
             programs.bash.loginShellInit = "elmer-wsl-welcome";
 
+            nixpkgs.overlays = [ inputs.elmer.overlay ];
+
             # When the config is built from a flake, the NIX_PATH entry of nixpkgs is set to its flake version.
             # Per default the resulting systems aren't flake-enabled, so rebuilds would fail.
             # Note: This does not affect the module being imported into your own flake.
@@ -73,7 +75,6 @@
             system = "x86_64-linux";
             modules = [
               self.nixosModules.default
-              { nixpkgs.overlays = [ inputs.elmer.overlay ]; }
               (config { })
             ];
           };
diff --git a/modules/build-tarball.nix b/modules/build-tarball.nix
index 7a1b1475..4093cac5 100644
--- a/modules/build-tarball.nix
+++ b/modules/build-tarball.nix
@@ -12,7 +12,9 @@ let
     # https://github.com/nix-community/NixOS-WSL
 
     { config, lib, pkgs, ... }:
-
+    let
+      elmerfem = import <elmerfem>;
+    in
     {
       imports = [
         # include NixOS-WSL modules
@@ -24,6 +26,8 @@ let
       wsl.elmer.enable = true;
       ${lib.optionalString (!config.wsl.nativeSystemd) "wsl.nativeSystemd = false;"}
 
+      nixpkgs.overlays = [ elmerfem.overlay ];
+
       # This value determines the NixOS release from which the default
       # settings for stateful data, like file locations and database versions
       # on your system were taken. It's perfectly fine and recommended to leave
@@ -78,8 +82,9 @@ in
           --system ${config.system.build.toplevel} \
           --substituters ""
 
-        echo "[Elmer-WSL] Adding channel..."
+        echo "[Elmer-WSL] Adding channels..."
         nixos-enter --root "$root" --command 'HOME=/root nix-channel --add https://github.com/ElmerCSC/Elmer-WSL/archive/refs/heads/main.tar.gz elmer-wsl'
+        nixos-enter --root "$root" --command 'HOME=/root nix-channel --add https://github.com/ElmerCSC/elmerfem/archive/refs/heads/devel.tar.gz elmerfem'
 
         echo "[Elmer-WSL] Adding default config..."
         ${if cfg.configPath == null then ''